Surface Passivation of Silicon Solar Cells by Amorphous Silicon/Silicon Nitride Dual Layers

We have investigated surface passivation of silicon by a dual structure consisting of a hydrogenated amorphous silicon thin film capped by a silicon nitride anti-reflection layer, both layers deposited by plasma enhanced chemical vapor deposition. The results show that a synergetic effect on the surface passivation properties is obtained from such a dual structure. Moreover, we find that the surface passivation can be significantly enhanced after a short anneal for temperatures up to about 500 °C, whereas anneals at higher temperatures result in degradation of the passivation properties. From nuclear reaction analyses of the as-deposited and annealed structures, the enhanced surface passivation experienced after annealing is indicated to be due to hydrogen release from the structure towards the silicon substrate, possibly followed by a redistribution of hydrogen and subsequent passivation of silicon dangling bonds in the sub-interface region.